JP2016114639A - Intermediate transfer belt and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt that offers high transferability to an image carrier having an irregular surface, and to provide an image forming device having the same.SOLUTION: An intermediate transfer belt consists of at least two layers comprising a base material layer and an elastic layer made of a rubber composition, and satisfies the following conditional expression (1): 1.30≤[Log(ρv100)/Log(ρv1000)]≤2.50 ...(1), where ρv100 [Ωcm] represents a volumetric resistivity as measured while a voltage of 100 V is applied to the intermediate transfer belt in a thickness direction thereof, and ρv1000 [Ωcm] represents a volumetric resistivity as measured while a voltage of 1000 V is applied to the intermediate transfer belt in the thickness direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an intermediate transfer belt and an image forming apparatus. More specifically, the present invention relates to an intermediate transfer belt applied to an electrophotographic image forming apparatus and an image forming apparatus including the intermediate transfer belt.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, for example, an electrostatic latent image formed on an electrostatic latent image carrier (photosensitive member) is visualized with toner, and the obtained toner image is temporarily transferred to an intermediate transfer belt. The toner image on the intermediate transfer belt is transferred onto an image support such as paper.
As described above, as an intermediate transfer belt applied to an image forming apparatus, there is one in which an elastic layer made of a rubber composition is formed on the surface of a base material layer (see, for example, Patent Document 1). . According to the image forming apparatus provided with such an intermediate transfer belt, the intermediate transfer belt can follow the image support member even when the image support member has an uneven surface such as embossed paper. Therefore, it is expected that good transferability to the image support can be obtained, and thus a high-quality visible image can be obtained.

  However, it has been clarified that an image forming apparatus using an intermediate transfer belt having an elastic layer has a problem that a high-quality visible image cannot be obtained depending on an image pattern of a visible image to be formed. Such a problem is remarkable when the visible halftone image to be formed includes a black halftone image.

Japanese Patent No. 3248455

  As a result of intensive studies by the inventors of the present invention based on the above circumstances, the problem of the image forming apparatus having the intermediate transfer belt having the conventional elastic layer is that the elastic layer is provided. Was found as a result of further investigation by the present inventors in order to solve the problem, and the purpose was to find an image support having irregularities. It is an object of the present invention to provide an intermediate transfer belt capable of obtaining high transferability and an image forming apparatus provided with the intermediate transfer belt.

The intermediate transfer belt of the present invention is an intermediate transfer belt comprising at least a base layer and an elastic layer made of a rubber composition.
When the volume resistivity when a voltage of 100 V is applied in the thickness direction of the intermediate transfer belt is ρv100 [Ω · cm], and the volume resistivity when a voltage of 1000 V is applied is ρv1000 [Ω · cm], The following relational expression (1) is satisfied.

Relational expression (1):
1.30 ≦ [Log (ρv100) / Log (ρv1000)] ≦ 2.50

  In the intermediate transfer belt of the present invention, it is preferable that the elastic layer has a thickness of 50 μm or more and 300 μm or less.

  An image forming apparatus according to the present invention includes the above-described intermediate transfer belt.

  According to the intermediate transfer belt of the present invention, it has a base material layer and an elastic layer made of a rubber composition, and the volume resistivity has a specific voltage dependency. Therefore, high transferability can be obtained for an uneven image support regardless of the image pattern to be transferred to the image support.

Since the image forming apparatus of the present invention is provided with the intermediate transfer belt of the present invention, the intermediate transfer belt has an uneven image support regardless of the image pattern to be transferred to the image support. On the other hand, high transferability is obtained. Therefore, according to the image forming apparatus of the present invention,
A high-quality visible image can be formed on an uneven image support.

FIG. 3 is a partial cross-sectional view illustrating an example of a configuration of an intermediate transfer belt according to the present invention. 1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus of the present invention.

  Embodiments of the present invention will be described below.

[Intermediate transfer belt]
The intermediate transfer belt of the present invention is applied to an electrophotographic image forming apparatus and comprises at least two layers of a base material layer and an elastic layer.
Since the intermediate transfer belt has an elastic layer, the intermediate transfer belt has elasticity. Therefore, even if the image support has irregularities on the surface on which a visible image is to be formed, the image support It will have follow-up ability to the body.

  In the intermediate transfer belt of the present invention, the surface of the intermediate transfer belt (the surface on which the toner image to be transferred to the image support is formed) is constituted by the surface of the elastic layer from the viewpoint of followability to the image support. It is preferred that

  The intermediate transfer belt of the present invention has a volume resistivity of ρv100 [Ω · cm] when a voltage of 100 V is applied in the thickness direction of the intermediate transfer belt, that is, the lamination direction of the base material layer and the elastic layer. When the volume resistivity when a voltage of 1000 V is applied in the thickness direction is ρv1000 [Ω · cm], the following relational expression (1) is satisfied.

Relational expression (1):
1.30 ≦ [Log (ρv100) / Log (ρv1000)] ≦ 2.50

  Here, [Log (ρv100) / Log (ρv1000)] according to the relational expression (1) is an index indicating the voltage dependency of the volume resistivity of the intermediate transfer belt. In the intermediate transfer belt, [Log (ρv100) ) / Log (ρv1000)] increases as the voltage dependency of the volume resistivity increases.

Since the intermediate transfer belt satisfies the above relational expression (1), it is not necessary to apply a high voltage to flow a desired transfer current, and the transfer current can be easily controlled. Therefore, a transfer current having a desired magnitude can be passed between the intermediate transfer belt and the image support with a low voltage.
More specifically, in the image forming apparatus, when a voltage is applied to the intermediate transfer belt, a transfer current flows between the intermediate transfer belt and the image support to generate a transfer electric field. The upper toner is transferred to the image support. Further, between the intermediate transfer belt and the image support, it is necessary to control a transfer current having a magnitude of several microamperes by adjusting the magnitude of the voltage applied to the intermediate transfer belt. . Thus, if the intermediate transfer belt satisfies the above relational expression (1), the toner (the toner constituting the toner image formed on the intermediate transfer belt) is more than the intermediate transfer belt. A transfer current of a required magnitude can be passed without applying a high voltage that would be charged, and the magnitude of the transfer current can be reliably controlled by the voltage applied to the intermediate transfer belt. Can do.

On the other hand, when [Log (ρv100) / Log (ρv1000)] is less than 1.30, the intermediate transfer belt has a small voltage dependency of the volume resistivity. In order to pass a desired transfer current between the two, it is necessary to apply a high voltage. Therefore, particularly when a black halftone image is formed, that is, when there is a sparse portion of black toner having a small resistance value in the toner image formed on the intermediate transfer belt, the toner is injected with charge. As a result, the toner charge amount is reduced, and in the obtained visible image, a black halftone image is poorly transferred (raised).
If [Log (ρv100) / Log (ρv1000)] exceeds 2.50, the intermediate transfer belt has a large voltage dependency of the volume resistivity, and it is difficult to control the transfer current. Become. For this reason, the transfer electric field generated between the intermediate transfer belt and the image support becomes unstable, so that transfer defects (roughness) of a low-density halftone image tend to occur in the obtained visible image.

The volume resistivity ρv100 and the volume resistivity ρv1000 are values measured using a resistance measuring instrument.
Specifically, using a resistance measuring instrument “HIRESTA IP / HR probe” (manufactured by Mitsubishi Chemical Corporation), an intermediate transfer belt cut to have a width of 360 mm is used as a measurement sample. At a total of 12 places, 3 places at equal pitches in the width direction and 4 places in the length direction, a desired voltage (specifically, 100 V) in the thickness direction of the measurement sample (the lamination direction of the base material layer and the elastic layer). Or a voltage obtained by measuring the volume resistivity 10 seconds after the start of voltage application and calculating the average value. Here, the voltage is applied to the measurement sample by bringing the measurement sample into contact with each of these two electrodes between the two electrode plates of the resistance measuring device.

Specifically, the intermediate transfer belt of the present invention is formed by forming an elastic layer 3 on a base material layer 2 as shown in FIG.
In the example of this figure, the intermediate transfer belt 1 has an endless belt shape in which a base material layer 2 is a base material made of a seamless belt.

(Base material layer)
The base material layer 2 is preferably made of a resin composition in which a conductive filler is dispersed in a resin component.

  As the resin component constituting the base material layer 2, from the viewpoint of mechanical strength and durability, polyimide resin (PI), polyamideimide resin (PAI), polyphenylene sulfide resin (PPS), and polyether ether ketone resin (PEEK) Super engineering plastics such as are preferred.

  As the conductive filler constituting the base material layer 2, a conductive filler made of carbon black, carbon nanotube, carbon nanofiber, or the like is preferable.

  In the base material layer 2, the content ratio of the conductive filler is appropriately determined in consideration of the type of the resin component, the thickness of the base material layer 2, the configuration of the elastic layer 3, and the like.

  Moreover, the base material layer 2 may have a single layer structure as shown in FIG. 1, or may have a multi-layer structure in which two or more layers are laminated.

  The thickness (layer thickness) of the base material layer 2 is preferably 50 to 250 μm from the viewpoints of mechanical strength and manufacturing cost.

(Elastic layer)
The elastic layer 3 is made of a rubber composition, and the rubber composition constituting the elastic layer 3 is preferably one in which a conductive filler is dispersed in a rubber component.
According to the rubber composition constituting the elastic layer 3 in which the conductive filler is dispersed, the volume resistivity of the intermediate transfer belt 1 (specifically, by adjusting the content ratio of the conductive filler) Specifically, the volume resistivity ρv100 and the volume resistivity ρv1000) can be easily controlled.

  Although it does not specifically limit as a rubber component which comprises the elastic layer 3, For example, crosslinked rubber materials, such as chloroprene rubber (CR), nitrile rubber (NBR), epichlorohydrin rubber (ECO), are mentioned. These may be used alone or in combination of two or more.

  As the conductive filler constituting the elastic layer 3, carbon black and carbon nanotubes are preferable from the viewpoints of electronic conductivity and volume resistivity control of the intermediate transfer belt 1.

  In the elastic layer 3, the content ratio of the conductive filler is appropriately determined in consideration of the type of the rubber component, the thickness of the elastic layer 3, the configuration of the base material layer 2, and the like.

  The thickness (layer thickness) of the elastic layer 3 is preferably 50 μm or more and 300 μm or less, and more preferably 200 μm or more and 300 μm or less.

When the thickness of the elastic layer 3 is 50 μm or more and 300 μm or less, the intermediate transfer belt 1 has a high transfer function.
Further, when the elastic layer 3 has a thickness of 200 μm or more, a visible image to be formed includes a solid image with a high toner adhesion amount (a solid image formed by superimposing a plurality of toner images). In this case, the intermediate transfer belt 1 can provide higher transferability to the image support.

On the other hand, when the thickness of the elastic layer 3 is too small, the intermediate transfer belt 1 does not have sufficient elasticity, and as a result, good transferability to an image support having irregularities cannot be obtained. There is a fear.
If the elastic layer 3 is excessively thick, the transfer electric field generated between the intermediate transfer belt 1 and the image support is excessively widened. As a result, the image is disturbed and a high-quality visible image is formed. There is a risk that it will not be obtained.

  Further, as shown in FIG. 1, when the surface of the elastic layer 3 constitutes the surface of the intermediate transfer belt 1 as shown in FIG. 1, the friction coefficient is adjusted from the viewpoint of the transfer function. It is preferable. The friction coefficient of the surface of the elastic layer 3 is preferably 0.3 or more and 0.7 or less.

  In the intermediate transfer belt 1 having such a configuration, for example, by adjusting the content ratio of the conductive agent in the base material layer 2 and the content ratio of the conductive filler in the elastic layer 3, the volume resistivity (specifically, volume The resistivity ρv100 and the volume resistivity ρv1000) are controlled to satisfy the above relational expression (1).

[Method of manufacturing intermediate transfer belt]
The intermediate transfer belt 1 is, for example, coated on the base material constituting the base material layer 2 by applying an elastic layer forming coating solution for forming the elastic layer 3 by dipping coating, and drying the formed coating film. It can manufacture by surface-treating as needed.
As the substrate, a resin seamless belt containing a conductive agent (conductive filler) can be used.
As the elastic layer forming coating solution, for example, a solution prepared by dissolving a mixture of a rubber material and a conductive filler in an organic solvent such as toluene can be used.
Examples of the surface treatment include light irradiation treatment.

  According to the intermediate transfer belt 1 having such a configuration, the base layer 2 and the elastic layer 3 made of a rubber composition have a volume resistivity having a specific voltage dependency, specifically the above-described one. Since the relational expression (1) is satisfied, a transfer current having a desired magnitude can be supplied at a low voltage. Therefore, high transferability can be obtained for an uneven image support regardless of the image pattern to be transferred to the image support.

[Image forming apparatus]
The intermediate transfer belt as described above can be suitably used for various known electrophotographic image forming apparatuses such as a monochrome image forming apparatus and a full color image forming apparatus.

  FIG. 2 is an explanatory sectional view showing an example of the configuration of an image forming apparatus provided with the intermediate transfer belt of the present invention.

  This image forming apparatus includes a plurality of sets of image forming units 20Y, 20M, 20C, and 20Bk and an intermediate transfer that transfers toner images formed in these image forming units 20Y, 20M, 20C, and 20Bk onto an image support P. And a fixing device 30 that performs a fixing process to obtain a toner layer by fixing the toner image by heating and pressing the image support P.

  The image forming unit 20Y forms a yellow toner image, the image forming unit 20M forms a magenta toner image, and the image forming unit 20C forms a cyan toner image. At 20 Bk, a black toner image is formed.

  The image forming units 20Y, 20M, 20C, and 20Bk give a uniform potential to the photoreceptors 11Y, 11M, 11C, and 11Bk that are electrostatic latent image carriers and the surfaces of the photoreceptors 11Y, 11M, 11C, and 11Bk. Charging means 23Y, 23M, 23C, 23Bk; exposure means 22Y, 22M, 22C, 22Bk for forming electrostatic latent images of a desired shape on the uniformly charged photoreceptors 11Y, 11M, 11C, 11Bk; Developing means 21Y, 21M, and 21C for developing toner images (specifically, yellow toner, magenta toner, cyan toner, and black toner) onto the photoreceptors 11Y, 11M, 11C, and 11Bk to visualize electrostatic latent images. , 21Bk, and cleaning means 25Y, 25 for collecting residual toner remaining on the photoreceptors 11Y, 11M, 11C, 11Bk after the primary transfer. Are those comprising 25C, and 25Bk.

  The intermediate transfer unit 10 transfers the toner images formed by the intermediate transfer belt 16 that circulates and the image forming units 20Y, 20M, 20C, and 20Bk to the intermediate transfer belt 16, and primary transfer rollers 13Y as primary transfer units. Secondary transfer as secondary transfer means for transferring the chromatic toner image transferred onto the intermediate transfer belt 16 by the 13M, 13C, 13Bk and the primary transfer rollers 13Y, 13M, 13C, 13Bk onto the image support P. A roller 13A and a cleaning unit 12 that collects residual toner remaining on the intermediate transfer belt 16 are provided.

The intermediate transfer belt 16 is an intermediate transfer belt according to the present invention, and is an endless belt that is stretched around a plurality of support rollers 16a to 16d and is rotatably supported.
Here, the intermediate transfer belt 16 has an elastic layer made of a rubber composition formed on a base material layer, and satisfies the relational expression (1).

The color toner images formed by the image forming units 20Y, 20M, 20C, and 20Bk are sequentially transferred onto the rotating intermediate transfer belt 16 by the primary transfer rollers 13Y, 13M, 13C, and 13Bk, and superimposed color. An image is formed. The image support P accommodated in the paper feed cassette 41 is fed by the paper feed / conveyance means 42, passes through a plurality of intermediate rollers 44a to 44d, and a registration roller 46, and then a secondary transfer roller 13A as a secondary transfer means. The color images are transferred onto the image support P at once.
The image support P to which the color image has been transferred is subjected to fixing processing by a fixing device 30 equipped with a heat roller fixing device, and is sandwiched between paper discharge rollers and placed on a paper discharge tray outside the apparatus.
On the other hand, after the color image is transferred to the image support P by the secondary transfer roller 13A, the residual toner is removed by the cleaning unit 12 from the endless intermediate transfer belt 16 from which the image support P is separated by curvature.

  Since the image forming apparatus as described above includes the intermediate transfer belt of the present invention, the intermediate transfer belt has an uneven image support regardless of the image pattern to be transferred to the image support. High transferability can be obtained. Therefore, according to the image forming apparatus of the present invention, the intermediate transfer belt has high durability and has an excellent transfer function. A visible image can be formed.

(Developer)
The developer used in the image forming apparatus of the present invention may be a one-component developer using magnetic or non-magnetic toner, or may be a two-component developer in which a toner and a carrier are mixed.
The toner constituting the developer is not particularly limited, and various known toners can be used. For example, a so-called polymerized toner obtained by a polymerization method having a volume-based median diameter of 3 to 9 μm can be used. It is preferable to use it. By using the polymerized toner, high resolution and stable image density can be obtained in the formed visible image, and the occurrence of image fog is extremely suppressed.

The carrier in the case of constituting the two-component developer is not particularly limited, and various known ones can be used. For example, the volume-based median diameter is 30 to 65 μm, and the magnetization is 20 to 70 emu. A ferrite carrier comprising / g of magnetic particles is preferred.
When a carrier with a volume-based median diameter of less than 30 μm is used, carrier adhesion may occur and a white-out image may be generated. When a carrier with a volume-based median diameter of greater than 65 μm is used, There may occur a case where an image having a uniform image density is not formed.

(Image support)
As the image support P used in the image forming apparatus of the present invention, coated paper such as plain paper, fine paper, art paper or coated paper from thin paper to thick paper, commercially available Japanese paper or postcard paper Various examples such as embossed paper, plastic film for OHP, and cloth can be given, but the invention is not limited to these.
As the image support P used in the image forming apparatus of the present invention, those having irregularities such as embossed paper, Japanese paper and cloth are suitable.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

[Production Example 1 of Intermediate Transfer Belt]
(1) Preparation of base material layer A 60 μm-thick polyimide seamless belt containing 8% by mass of a conductive filler made of carbon nanofibers is prepared, and the seamless belt constitutes the base material layer of the intermediate transfer belt. The substrate was [1].

(2) Formation of elastic layer 80 parts by mass of chloroprene rubber as a rubber material and 20 parts by mass of carbon black “Asahi Thermal” (manufactured by Asahi Carbon) as a conductive filler are mixed, and the resulting mixture is dissolved in toluene. By doing this, the elastic layer forming coating solution [1] was prepared.
Then, the elastic layer forming coating solution [1] is applied to the outer peripheral surface of the substrate [1] by the dipping coating method, and the formed coating film is dried. By performing light irradiation treatment according to the irradiation conditions, an elastic layer having a thickness (film thickness) of 200 μm was formed, and thus an intermediate transfer belt [1] was obtained.
About the obtained intermediate transfer belt [1], using a resistance measuring device “HIRESTA IP / HR probe” (manufactured by Mitsubishi Chemical Corporation), volume resistivity ρv100 and volume resistivity ρv1000 are measured by the above methods, Based on the obtained volume resistivity ρv100 and volume resistivity ρv1000, the value of [Log (ρv100) / Log (ρv1000)] was calculated. The results are shown in Table 1.

(Light irradiation conditions)
Type of light source: High-pressure mercury lamp “H04-L41” (made by Eye Graphics)
Light irradiation distance (distance from irradiation port to coating film surface): 100 mm
Irradiation quantity: 1 J / cm ²
Irradiation time (time for rotating the substrate): 240 seconds

[Production Examples 2 to 9 of Intermediate Transfer Belt]
In the process of forming the elastic layer of Production Example 1 of the intermediate transfer belt, an elastic layer forming coating solution is prepared according to the prescription in Table 1, and the elastic layer having the thickness shown in Table 1 is prepared using the elastic layer forming coating solution. The intermediate transfer belt [2] to the intermediate transfer belt [9] were obtained in the same manner as in the production example 1 of the intermediate transfer belt except that.
For the obtained intermediate transfer belt [2] to intermediate transfer belt [9], the value of [Log (ρv100) / Log (ρv1000)] was calculated by the same method as in Production Example 1 of the intermediate transfer belt. The results are shown in Table 1.

[Examples 1 to 5 and Comparative Examples 1 to 4]
The intermediate transfer belt [1] to the intermediate transfer belt [9] are mounted as an intermediate transfer belt of an image forming apparatus “KONICA Minolta bizhub PRESS C8000” (manufactured by Konica Minolta), and embossed paper (Rezac 302g paper) as an image support. The following evaluation tests were conducted using The results are shown in Table 1.

(Image quality evaluation of blue solid images)
In the image forming apparatus, an operation of outputting a blue solid image obtained by the cyan toner and the magenta toner image is performed, and a toner image to be transferred to the image support (specifically, a cyan toner image and a magenta toner image) The amount of toner on the intermediate transfer belt on which the toner image is superimposed (the amount of toner on the belt before transfer) and the amount of toner on the intermediate transfer belt after the toner image is transferred to the image support ( The amount of toner on the belt after transfer) was measured, and the transfer rate was calculated by the following formula (1). Then, the image quality of the blue solid image was evaluated according to the following evaluation criteria.

(Quality evaluation standard for blue solid images)
“◎”: When the transfer rate is 95% or more “◯”: When the transfer rate is 93% or more and less than 95% “Δ”: The transfer rate is 90% or more and less than 93% Case “x”: When the transfer rate is less than 90% and the color is different

(Quality evaluation of black halftone image)
In the image forming apparatus, an operation was performed to output a black halftone image on the entire surface of the embossed paper, and the obtained visible image was visually confirmed to evaluate the image quality of the black halftone image according to the following evaluation criteria. did.

(Quality evaluation of black halftone image)
“◎”: When there is no unevenness “○”: When there is unevenness but there is no practical problem “X”: When there is unevenness and there is a practical problem

  In Table 1, “carbon black (1)” is “Asahi Thermal” manufactured by Asahi Carbon Co., and “carbon black (2)” is “special black 4” manufactured by Degussa. In the table, “tetrabutylammonium hydrogen sulfate” is an ionic conductive agent.

  From the results shown in Table 1, according to the image forming apparatuses according to Examples 1 to 5, a two-layer overlapping solid image having a high toner adhesion amount (specifically, an image support having irregularities from the intermediate transfer belt) Is a solid image formed by superimposing a magenta toner image and a cyan toner image) and a black halftone image with a low toner adhesion amount, and can be transferred with high transferability. It was confirmed that

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 2 Base material layer 3 Elastic layer 10 Intermediate transfer part 11Y, 11M, 11C, 11Bk Photoconductor 12 Cleaning means 13Y, 13M, 13C, 13Bk Primary transfer roller 13A Secondary transfer roller 16 Intermediate transfer belts 16a to 16d Rollers 20Y, 20M, 20C, 20Bk Image forming units 21Y, 21M, 21C, 21Bk Developing means 22Y, 22M, 22C, 22Bk Exposure means 23Y, 23M, 23C, 23Bk Charging means 25Y, 25M, 25C, 25Bk Cleaning means 30 Fixing device 41 Paper feed cassette 42 Paper feed conveyance means 44a, 44b, 44c, 44d Paper feed roller 46 Registration roller N1 Fixing nip P Image support

Claims (3)

In an intermediate transfer belt comprising at least two layers of a base material layer and an elastic layer made of a rubber composition,
When the volume resistivity when a voltage of 100 V is applied in the thickness direction of the intermediate transfer belt is ρv100 [Ω · cm], and the volume resistivity when a voltage of 1000 V is applied is ρv1000 [Ω · cm], An intermediate transfer belt characterized by satisfying the following relational expression (1).
Relational expression (1):
1.30 ≦ [Log (ρv100) / Log (ρv1000)] ≦ 2.50   The intermediate transfer belt according to claim 1, wherein the elastic layer has a thickness of 50 μm or more and 300 μm or less.   An image forming apparatus comprising the intermediate transfer belt according to claim 1.

Images